How to see both the wood and the trees

Clive Aslet

12:01AM BST 29 Oct 2006

Clive Aslet reviews Woodlands by Oliver Rackham

The best books shake your ideas up and show that you knew an awful lot less than you thought you did. This is one of them. It turns out that nearly all the received wisdom about trees in Britain is wrong.

Take the most basic facts about how they receive their nutrients from the soil. Minerals are sucked up through the root system – every school child knows that. Not so. Trees wouldn't get nearly enough nourishment were it not for the fungi that co-exist with them. The hyphae of a fungus are much finer than root hairs; a seedling will die if it fails to find a friendly fungus to cuddle up with.

Forest fires are terrifying phenomena, but don't worry unduly: some trees are 'fire-adapted' and thrive after competing species have been burnt away. This is true of Aleppo pines in the Mediterranean and Australian eucalyptus. Native British woodland simply doesn't burn (too much soggy leaf litter) unlike the conifer plantations that used to be laid down by the Forestry Commission. For this reason, it is implausible to think that early or even medieval man cleared forest by means of combustion, despite place names such as Burnt Norton.

'To get an English wood to burn the trees have to be cut down, carried to a fire site, cut up, and densely stacked before a fire in one log will spread into the next.' It's obvious, if you think about it. But my goodness, those Stone Age people were handy with their axe heads. Britain was denuded of most of its primeval forest thousands of years ago. There wasn't much left by the time of the Domesday Book. Another myth – of a Britain studded with immense trees into the Tudor period – falls.

Oliver Rackham is the only person with the depth of knowledge to write this book. It is a bravura performance for the 100th title in the New Naturalist Series. My jaw dropped so often while reading it that it aches. Aperçus are thrown off with almost casual aplomb. Have you ever thought about how trees are represented in landscape paintings? Even country-loving Gainsborough could hardly paint them in such a way that individual species can be identified by Dr Rackham.

Then there is that old canard about Nelson's navy. It turns out that bark, to tan saddle leather and boots, was just as valuable as timber. While the Navy complained about a shortage of trees, commercial shipbuilders seemed to manage perfectly well. 'The Navy was short of money rather than short of trees.' Besides, of the 3,000 loads of timber 'needed' to build a 74-gun ship, Dr Rackham calculates that as much of two-thirds may have gone missing in the form of perks. There are a lot of soundly built wooden houses around dockyards. While almost every owner of an ancient timber-framed house believes that some of his beams come from old ships, this is rarely the case. Ships used the wrong sort of timbers.

Tudor carpenters made do with rather smaller trees than one might have thought. They were no longer than 14ft in the case of one Weald of Sussex house; a substantial farmhouse outside East Bergholt in Suffolk, owned by the National Trust, was built of 50-acres' worth of three-year old trees, along with some reused timbers and offcuts. Not all the timber was oak.

Woodland was simply left to regenerate after harvesting. After all, it had managed to get along pretty well by itself for centuries, surviving in all sorts of unpropitious locations. An instructive contrast, we are left to conclude, with what Dr Rackham calls the 'locust years' of 1950-1975, with their misguided devotion to monocultures of sitka spruce.

What is Dr Rackham's prescription for the future? Be more careful in the choice of the species we plant: even the supposedly natural woodland that is now in vogue is apt to contain the wrong sort of trees. Battle against the grey squirrel: by stealing hazel nuts while they are green this American arriviste could jeopardise the very existence of native hazel. But the contribution that tree-planting can make to counteract global warming is doubtful.

We must humble ourselves before the subtle workings of nature, which should, where possible, be allowed to get on by themselves. As Dr Rackham concludes: 'The time for playing God is over.' It is a remarkable book.